The permeation of oxygen ions through ceramic ion transport membranes is the basis for a variety of gas separation devices and oxidation reactor systems operating at high temperatures in which permeated oxygen is recovered on the permeate side as a high purity oxygen product or is reacted on the permeate side with oxidizable compounds to form oxidized or partially oxidized products. The practical application of these gas separation devices and oxidation reactor systems requires membrane assemblies having large surface areas, gas distribution systems to contact feed gas with the feed sides of the membranes, and product collection systems to withdraw product gas from the permeate sides of the membranes. These membrane assemblies may comprise a large number of individual membranes arranged and assembled into modules having appropriate gas flow piping to introduce feed gas into the modules and withdraw product gas from the modules.
Ion transport membranes may be fabricated in either planar or tubular configurations. In the planar configuration, multiple flat ceramic plates are fabricated and assembled into stacks or modules having piping systems to pass feed gas over the planar membranes and to withdraw product gas from the permeate side of the planar membranes. In tubular configurations, multiple ceramic tubes may be arranged in bayonet or shell-and-tube configurations with appropriate tube sheet assemblies to isolate the feed and permeate sides of the multiple tubes.
The individual membranes used in planar or tubular module configurations typically comprise very thin layers of active membrane material supported on material having large pores or channels that allow gas flow to and from the surfaces of the active membrane layers. Each active ceramic membrane operates in a highly-reactive chemical and electrochemical environment, and the presence of certain contaminants in the hot feed gas in this environment may adversely affect the membrane stoichiometry and operating efficiency. The adverse results may differ depending on whether the membrane is operated in gas separation or oxidation service. The potential operating problems caused by these phenomena can have a significant negative impact on the purity of recovered products and on membrane operating life.
The solid ion-conducting metallic oxide materials used in these membrane modules may degrade in the presence of volatile gas-phase contaminants at the high operating temperatures required to effect ion conduction, thereby reducing the ability of the membranes to conduct or permeate oxygen ions. Because of this potential problem, there is a need in the art for methods to control certain contaminants in the feed gas to the membrane modules and in reactive gases within the membrane modules to ensure the successful operation of ion-conducting metallic oxide membrane systems. These needs are addressed by embodiments of the present invention as disclosed below and defined by the claims that follow.